1. Field of the Invention
The present invention relates to a novel fluorine-containing copolymer. More particularly, it relates to a copolymer for an elastomer having excellent low temperature resistance and oil resistance which comprises specific contents of ethylene units and specific fluorovinyl ether units.
2. Description of the Prior Arts
It has been known to provide fluorine-containing elastomers from copolymers made of vinylidene fluoride/hexafluoropropylene; tetrafluoroethylene/propylene; tetrafluoroethylene/perfluoroalkyl vinyl ether; or vinylidene fluoride/perfluoroalkyl vinyl ether. These elastomers have been used as useful elastomers. Such elastomers have excellent characteristics which could not be imparted by hydrocarbon type elastomers in view of heat resistance, oil resistance and chemical resistance, however they have not satisfactory low temperature performance.
On the other hand, it has been known that fluorine-containing elastomers having siloxane bonds or phosphazene bonds in a main chain and fluorinated alkyl groups or fluorinated alkoxy groups as branched chains have excellent low temperature resistance. Such elastomers have, however, inferior chemical resistance and heat resistance to those of the above-mentioned fluorocarbon type fluorine-containing elastomers.
The fluorocarbon type elastomers having excellent low temperature resistance together with excellent heat resistance and chemical resistance have not been found through such elastomers have been desired in the fields of automobiles and airplanes.